\section{Assebly}
\subsection{Equipment Assembly Modelling Options}
The best approach to modelling equipment depends on your requirement for data to be extracted from the model.

The simplest approach to modelling Equipment is to create an Equipment element in DESIGN, and create a collection of primitives and nozzles under the Equipment element. In this case, no Design Template is used. This approach may be suitable for unique Equipment items that are not reused in the same project or in other projects.

In order to model an Equipment item containing Pipe and HVAC connections, and support steelwork, where the Equipment can be selected via an Equipment specification, it is necessary to create an Equipment Template.
\subsection{Equipment Spatial Associations}
The Equipment Associations utility allows users to apply geometrical constraints between Equipment and its surroundings for subsequent design checking. An Equipment Association is a design rule that can be checked by the system. The system will report success if a design constraint is satisfied by the model, otherwise it will report a failure.

The Equipment Associations utility provides the ability to create, modify, delete and view details of Equipment Associations. A separate utility, called the Association Manager, is accessible from the DESIGN module, and allows users to view these associations. This is described in Association Manager.
\subsection{Configure the System}
There are three Project set up considerations for this utility. These are administration functions:

•  Loading equipment association definitions 

•  Management of stored associations 

•  Adding association features to equipment 

\subsection{Load Equipment Association Definitions}
This utility relies on a standard set of Association Definitions being loaded into the project. These are supplied as part of the standard Master project in Association World /AVEVA-Std-Association-Definitions, which includes the following Association Definitions:

•  /AV-STDMATE 

•  /AV-STDALIGN 

•  /AV-STDPARALLEL 

•  /AV-STDPARALLELOFFSET 

•  /AV-STDDISTANCE 

•  /AV-STDHORIZDIST 

•  /AV-STDABOVELINE 

•  /AV-STDELEVATION 

Normal users require only read access to these definitions, so it is recommended that a database containing these definitions is placed in a common Master project with other company standard data. This is an administrator function.
\subsection{Management of Stored Associations}
Each geometrical constraint is stored as an Association element. Association elements are stored in a DESI database under a world element of type Association World (ASSOWL). Each Association world can contain any number of Association Group elements (ASSOGP), which in turn contain Association elements (ASSOC).

Associations created by this utility are placed in Association Groups with the PURPOSE attribute set to ASEQ. Every time that an Association is created by this utility, the system searches for the first Association Group element that it can find with PURPOSE set to ASEQ. If the first group found cannot be written to by the user, the system searches for the next Association Group, and so on until an ASSOGP is found where the user can create an Association. This allows storage of Associations to be managed in several ways:

•  All Associations generated by this utility are put into one group - only recommended if there will be a small number of Associations of this type. 

•  Association Groups are locked to prevent any more Associations from being created in that location and new Association Groups are created to collect the next batch of Associations. 

•  Use Data Access Control to open certain Association Group elements for write access to certain users or groups of users.
\subsection{Add Association Features to Equipment} 
P-points, Design Points and P-lines can be selected as reference points for Associations. These can be picked in the 3D view when an Association is created.
It can be quite difficult to pick a particular graphical point in a 3D view where many elements are displayed. To make it easier to select reference points or lines to be used in an Association, it is recommended that Design Points are created in Design Templates, and P-points in catalogue items that identify themselves as connection points for Associations.
This can be achieved by creating Design Points or P-points with PURPOSE attribute set to a four character value where the first two characters are chosen by the person defining the point, and the last two characters must be 'FA'. For example, an Equipment may be created with three Association Design Points with PURPOSE attributes set to CLFA for centre-line, BOFA for bottom face and TOFA for top face. Any number of reference points can be created for each element, but it is recommended that only the most commonly used reference points on each type of Equipment or catalogue item are defined in this way, otherwise they will become difficult to identify in a 3D view.
\subsection{Create Equipment Association}
Begin by displaying the elements that will be related together with a geometric constraint.
In the Equipment Application, select Utilities > Equipment Associations from the main menu to start the Equipment Associations utility. The following window is displayed:

1.  Click Select Association Item to pick the primary member of this Association. 

2.  Select the type of geometric association required from the Make a new association list. The association types are described in Association Types. 

3.  Click Select new Association partner to select the other item in this geometrical relationship. 

4.  The list headed Participates in associations shows the Associations that the primary member participates in. These Associations can be modified or deleted by selecting a row in this list.  

\subsection{Association Types}
The following types of geometric constraints can be defined:
Mate Two faces are touching (coplanar) or separated by a given distance. Directions defined by the two face normals are parallel and in the opposite direction. 
Align Two faces are aligned (coplanar) or separated by a given distance. Directions defined by the two face normals are parallel and in the same direction. 
Parallel Two directions are parallel, pointing in the same direction or in opposed directions. 
Parallel Offset Two lines are parallel and separated by a given distance. 
True Distance Two points are coincident or separated by a given distance. 
Elevation The elevation of two points is separated by a given distance. 
Horizontal Distance One point is vertically above the other point, or separated in the horizontal plane by a given distance. 
Point above line A point is vertically above or below a line within a given tolerance. 

\section{Identify Reference Geometry}
When both the primary member and the partner member for this Association have been selected, the following window is displayed where you define details of the geometrical relationship between the two items:

